U.S. patent number 9,166,830 [Application Number 13/945,096] was granted by the patent office on 2015-10-20 for systems and methods utilizing adaptive envelope tracking.
This patent grant is currently assigned to Intel Deutschland GmbH. The grantee listed for this patent is Intel Mobile Communications GmbH. Invention is credited to Alexander Belitzer, Andrea Camuffo, Bernhard Sogl.
United States Patent |
9,166,830 |
Camuffo , et al. |
October 20, 2015 |
Systems and methods utilizing adaptive envelope tracking
Abstract
A communication system utilizing adaptive envelope tracking
includes a transmit path, a feedback receiver, a parameter
component and an envelope tracking component. The transmit path is
configured to generate a transmit signal. The feedback receiver is
configured to generate a feedback signal from the transmit signal.
The parameter component is configured to generate linearity
parameters from the feedback signal and the baseband signal. The
envelope tracking component is configured to generate a supply
control signal having time delay adjustments.
Inventors: |
Camuffo; Andrea (Munich,
DE), Belitzer; Alexander (Munich, DE),
Sogl; Bernhard (Unterhaching, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Intel Mobile Communications GmbH |
Neubiberg |
N/A |
DE |
|
|
Assignee: |
Intel Deutschland GmbH
(Neubiberg, DE)
|
Family
ID: |
52131451 |
Appl.
No.: |
13/945,096 |
Filed: |
July 18, 2013 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150023445 A1 |
Jan 22, 2015 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03F
1/3247 (20130101); H03F 1/0227 (20130101); H04L
27/04 (20130101); H03F 3/21 (20130101); H03G
3/30 (20130101); H04L 27/02 (20130101); H03F
1/0233 (20130101); H04L 25/03 (20130101); H03F
1/02 (20130101); H03F 2200/102 (20130101); H03F
2200/129 (20130101); H04L 25/03343 (20130101) |
Current International
Class: |
H04L
25/03 (20060101); H04L 27/02 (20060101); H03F
1/02 (20060101); H03F 1/32 (20060101) |
Field of
Search: |
;455/91,114.1,114.2,114.3,115.1,126,127.1,127.2 ;375/295,296 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Le; Thanh
Attorney, Agent or Firm: Eschweiler & Associates,
LLC
Claims
What is claimed is:
1. A communication system utilizing adaptive envelope tracking, the
system comprising: a transmit path configured to generate a
transmit signal from a baseband signal; a feedback receiver
configured to generate a feedback signal from the transmit signal;
a parameter component configured to generate linearity parameters
from the feedback signal; and an envelope tracking component
configured to generate a supply control signal having time delay
adjustments based on the linearity parameters.
2. The system of claim 1, further comprising a coupler configured
to provide a replica of the transmit signal to the feedback
receiver.
3. The system of claim 1, further comprising a DCDC supply
component configured to provide a supply signal according to the
supply control signal.
4. The system of claim 3, further comprising a power amplifier
powered by the supply signal and configured to amplify the transmit
signal from the transmit path, wherein the transmit signal includes
time distortions.
5. The system of claim 1, wherein the feedback signal includes real
and imaginary components.
6. The system of claim 1, wherein the feedback receiver is
configured to eliminate absolute phase from the feedback
signal.
7. The system of claim 1, wherein the linearity parameters include
one or more of an adjacent channel leakage ratio, an error vector
magnitude, amplitude modulation to amplitude modulation curves,
amplitude modulation to phase modulation curves, and time variant
distortion.
8. The system of claim 1, wherein the parameter component is
further configured to generate linearity parameters from the
baseband signal and the feedback signal.
9. The system of claim 1, wherein the envelope tracking component
includes a time delay block configured to generate the time delay
adjustments.
10. The system of claim 1, wherein the time delay adjustments
include a time delay amount and a direction.
11. The system of claim 1, wherein the envelope tracking component
is configured to generate an initial supply signal according to a
calibration of linearity and power consumption.
12. The system of claim 1, wherein the envelope tracking component
is configured to track the linearity parameters over successive
time periods in order to generate the time delay adjustments.
13. The system of claim 1, wherein the envelope tracking component
is configured to receive a sensor signal in order to generate the
time delay adjustments.
14. An envelope tracking system comprising: a first component
configured to generate a control signal that tracks amplitude
modulation according to a baseband signal and linearity parameters;
and a time delay component configured to generate time delay
adjustments for the control signal according to at least the
linearity parameters; and a parameter calculation component
configured to generate the linearity parameters at least partially
based on the baseband signal.
15. The system of claim 14, wherein the first component is
configured to generate the control signal by mapping the linearity
parameters and the baseband signal to isogain curves.
16. The system of claim 14, wherein the first component is
configured to generate the control signal by utilizing
predistortion coefficients.
17. A method of performing adaptive envelope tracking with time
delay tracking, the method comprising: generating an initial supply
control signal including a nominal time adjustment; obtaining one
or more linearity parameters for a current time period from a
feedback signal; determining a time delay adjustment based on the
linearity parameters upon the linearity parameters exceeding a
threshold value; and generating a control signal having the time
delay adjustment upon the linearity parameters exceeding a
threshold value.
18. The method of claim 17, wherein the linearity parameters
include one or more of an error vector magnitude and an adjacent
channel leakage ratio.
19. The method of claim 17, wherein the nominal time adjustment is
based on a compromise between linearity and power consumption.
20. The method of claim 17, further comprising generating the
feedback signal from a transmit signal prior to obtaining the one
or more linearity parameters.
Description
BACKGROUND
Communication systems utilize power amplifiers to boost signals for
prior to transmitting, such as transmitting via an antenna. Two
important characteristics for amplifiers used in such systems are
gain and power efficiency.
The gain of an amplifier is the measure of the ability of an
amplifier to increase an output signal from an input signal. It is
important that the gain be at the right value. Additionally, it is
important that the gain be relatively constant for varied input
values and frequencies. Variations in gain can lead to distorted
signals upon transmission. Thus, a relatively constant gain,
without variations according to input signal values, is needed.
The power efficiency is the ratio of output power to input power.
Some amplifiers may only be efficient when the input signal has a
high value. In others, the efficiency may depend on frequency.
A challenge faced by amplifier designers is to provide constant
gain while also having high power efficiency. Often, improving gain
comes at the expense of power efficiency and improving power
efficiency comes at the expense of not having a constant gain.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating a communication system
utilizing envelope tracking with time delay tracking.
FIG. 2 is a graph illustrating isogain curves and adjustments for a
power amplifier.
FIG. 3 is a graph illustrating an example of adaptive, iterative
envelope tracking through a series of time periods.
FIG. 4 is a block diagram illustrating an envelope tracking
component using isogain curves mapping in a communication
system.
FIG. 5 is a block diagram illustrating an envelope tracking
component using isogain curves and/or predistoriton coefficients in
a communication system.
FIG. 6 is a flow diagram illustrating a method of performing
adaptive envelope tracking with time delay tracking.
DETAILED DESCRIPTION
The present invention will now be described with reference to the
attached drawing figures, wherein like reference numerals are used
to refer to like elements throughout, and wherein the illustrated
structures and devices are not necessarily drawn to scale.
Systems and methods are disclosed that utilize adaptive envelope
tracking, including time domain tracking. They include
measuring/tracking one or more parameters of a replica transmit
signal to further configure a DCDC supply signal for a power
amplifier. The system measures a parameter, such as adjacent
linearity, channel leakage ratio (ACLR), error vector magnitude
(EVM) degradation, amplitude modulation to amplitude modulation
(AMAM) curves, amplitude modulation to phase modulation (AMPM)
curves, memory behavior and time variant distortion, and the like.
These measured parameters are utilized to adapt the envelope
tracking, including time alignment, accordingly.
Generally, envelope tracking (ET) is a technique where a power
amplifier is supplied through a fast DCDC converter, which has an
output voltage varying over time as a function of amplitude
modulation. The power amplifier is operated as closes as possible
to saturation during the modulation peaks and to lower voltages
when the instantaneous amplitude signal is low. As a result, power
amplifier efficiency is increased.
There are some challenges to envelope tracking. The gain of the
power amplifier is affected by the DCDC voltage. Thus, simply
following peaks of an amplitude modulation signal lead to gain
variations, which result in distortion. Furthermore, amplitude
modulation phase modulation (AM/PM) phenomena may take place, which
impairs modulation quality resulting in spurious emissions
(unwanted energy in neighboring channels) or error vector magnitude
(EVM) degradation.
It is noted that time alignment between the DCDC voltage and an
envelope of a signal in the RF path is important. This time
alignment is also referred to as synchronization. Any drift of
synchronization during operation causes unwanted signal distortion.
This unwanted signal distortion is not detectable in conventional
systems.
One technique to mitigate distortion to modulation signals is to
select a trajectory of a DCDC control voltage accurately so that
the gain stays constant. It is noted that as a signal level
increases and an amplifier approaches saturation, its instantaneous
gain diminishes. As stated above, the DCDC voltage is increased
when the amplitude modulation signal goes through a peak, however
increasing the DCDC voltage generally leads to a gain increase. By
combining these two effects, a cancellation can be obtained, thus
limiting unwanted distortion of the signal. For this technique to
work, AM/PM introduced by the power amplifier must be
negligible.
Another technique is to compensate AM/AM and AM/PM distortions by
adequately predistorting a supply input to the power amplifier.
This technique can utilize closed loop and open loop architectures.
Closed loop architectures need an extremely wide bandwidth in order
to not create excess noise at duplexer offset and, may not be
feasible. Open loop architectures need to know characteristics of a
power amplifier.
One approach to obtaining the power amplifier characteristics is to
utilize iso gain contours and knowledge of AM/AM and AM/PM curves
as a function of instantaneous DCDC voltage.
However, calibrating isogain contours is problematic. The prolong
calibration time for power amplifier calibration time, for example
at the factory. The isogain contours must be stored in a memory.
Further, the isogain contours are fixed for certain characteristics
of the power amplifier. If those characteristics change, the
isogain contours may not apply or match the current characteristics
of the power amplifier.
FIG. 1 is a block diagram illustrating a communication system 100
utilizing envelope tracking with time delay tracking. The system
100 learns and/or updates linearity parameters utilizing a feedback
receiver 114 to mitigate amplifier gain variations and power
consumption. The system 100 utilizes, for example, isogain contours
and predistortion coefficients, and the like to modify DC supply to
the power amplifier. Unlike the other techniques described above,
the envelope tracking of the system 100 is adaptive, thus it
adjusts over time.
The system 100 includes a baseband signal component 102, a transmit
component 108, a power amplifier 110, a coupler 112, an envelope
tracking component 104, a DCDC converter 106, a feedback receiver
114, and a parameter calculation component 116.
The baseband signal component 102 provides a baseband signal, x(t),
at its output. The baseband signal is received by the transmit
component 108. The transmit component 108 can include a digital
and/or analog transmit chain. The transmit component 108 generates
a modulation signal 124 from the baseband signal and provides the
modulation signal 124 to the power amplifier 110.
The power amplifier 110 generates a transmit signal, y(t), from the
modulation signal 124. The power amplifier 110 is supplied by a
DCDC supply signal 122, which varies according to envelope
tracking. The DCDC supply signal 122 is calibrated as described
below to include envelope tracking, including time delay tracking
or time synchronization.
The transmit signal, y(t), generally has some amount of distortion
present. The distortion is due to amplitude modulation to phase
modulation phenomena, amplitude modulation to amplitude modulation
phenomena, non-linearity or saturation of the amplifier 110,
inaccurate time alignment, and the like.
The coupler 112 generates a coupled transmit signal 118 from the
transmit signal, y(t). The transmit signal y(t) is provided by the
power amplifier 110. The coupled transmit signal 118 is an
attenuated replica of the transmit signal. The transmit signal
passes through the coupler and can be transmitted via an antenna
and/or other suitable mechanism (not shown).
The feedback receiver 114 demodulates and analyzes the transmit
signal in baseband. A feedback signal 126 is generated, also at the
baseband. In one example, the feedback signal 126 includes real and
imaginary components Real(y) and Imag(y).
The parameter calculation component 116 receives the feedback
signal 126 and the baseband signal 102 and develops a parameter
signal 120. Generally, the parameter calculation component 116
learns and/or updates linearity parameters for envelope tracking.
The parameters are learned/updated by comparing the baseband signal
102 and the feedback signal 126 and indicate linearity of the
transmit signal. These parameters are then utilized to generate the
parameter signal 120.
The parameter calculation component 116 is configured to measure
and/or identify the linearity parameters. These can include
indicators of linearity, including adjacent linearity, channel
leakage ratio (ACLR), error vector magnitude (EVM) degradation,
amplitude modulation to amplitude modulation (AMAM) curves,
amplitude modulation to phase modulation (AMPM) curves, memory
behavior and time variant distortion, and the like. The component
116 generates the parameter signal 120 having the measured and/or
identified parameters. The parameter signal 120, in one example,
can include coefficients related to time delay, time delays, and
the like. In another example, the parameters signal 120 only
includes measured linearity parameters for a current time period.
The parameter signal 120 facilitates alignment of the DCDC signal
122 with an RF envelope of the transmit signal.
Generally, the envelope tracking component 104 maps an amplitude of
the baseband signal 102 to the DCDC supply signal 122. The envelope
tracking component 104 provides a control signal 128 to the DCDC
supply 106, where the control signal 128 includes time delay
adjustment(s). The envelope tracking component 104 generates the
control signal 128 according to the baseband signal 102 and the
parameter signal 120. The baseband signal 102 facilitates mapping
to the amplitude of the baseband signal 102 and the parameter
signal 120 facilitates further adjustments based on measured
parameters, which are described in further detail below. The
control signal 128 facilitates alignment of the DCDC signal 122
with the RF envelope of the transmit signal.
In one example, the envelope tracking component 104 utilizes a
lookup table to generate the control signal 128. The one or more
parameters are utilized to look up a time delay adjustment, which
is incorporated into the control signal 128. The lookup table may
include coefficients and the like. In another example, coefficients
are learned and updated for each time slot or time period.
In another example, time delay adjustments are made using slow
learning without storing coefficients. In this example, initial
time slots start with high DCDC voltage and low envelope tracking
depth, which yields limited power efficiency but high gain. During
each slot, the linearity parameters of the signal 120 are observed
and the proximity to saturation is estimated. Then, the time delay
adjustment component of the signal 128 is adjusted accordingly.
In yet another example, the envelope tracking component 104
determines time delay adjustments. An initial or nominal time delay
is identified by calibration, and takes into account linearity and
energy consumption. The linearity parameters are compared with a
threshold value. On the parameter exceeding a threshold, the time
delay adjustment is altered in direction and/or amount. By
exceeding the threshold, the parameter and the transmit signal has
degraded beyond a limit.
The direction of the change in the adjustment 120 can be determined
by analyzing system characteristics and/or investigating parameter
trend progression over time. The characteristics include one or
more of temperature, antenna impedance, and the like. Such
characteristics can be provided from sensors and the like (not
shown). Otherwise, the direction is determined by whether the
adjustment 120 improves or degrades the parameter(s). If the
adjustment worsens the parameter, it can be assumed that the
direction is incorrect.
The DCDC component 106 generates the DCDC supply signal 122
according to the control signal 128. The DCDC supply signal 122
generally tracks the envelope of the transmit signal. The DCDC
supply signal 122 tracks or follows an amplitude modulation
component of the transmit signal so that the gain of the power
amplifier 110 is relatively constant.
Thus, the system 100 adaptively adjusts the DCDC supply signal for
the power amplifier 110 to mitigate linearity variations and power
consumption. Further, by adapting over time, the system 100 adapts
to varied operating system characteristics, including environmental
conditions and the like.
FIG. 2 is a graph 200 illustrating isogain curves and adjustments
for a power amplifier. The graph 200 is provided for illustrative
purposes. The power amplifier can include the power amplifier 110,
described above.
An isogain curve represents behavior of a power amplifier supplied
by a constant voltage. Generally, a power amplifier has a linear
region/range and a saturation region/range. In the linear region,
the output power has a linear relationship to the input power. In
the saturation region, the output power has a non-linear
relationship to the input power. An envelope tracking component,
such as component 104 described above, causes the DCDC supply to
the power amplifier to be compensated or predistorted in order to
provide a substantially linear gain.
The graph 200 includes an input voltage on an x-axis and an output
voltage on a y-axis. Curve 201 shows an example. In a base or
linear region, the output voltage is linear with respect to the
input voltage. However, in a saturation region, a non-linear
relationship is shown. At this point, the input voltage has reached
a saturation point. And, as a result, the output voltage doesn't
follow properly.
As described above, an adjustment or compensation is made in order
to provide a linear output voltage. In the system 100, described
above, the control signal causes the output voltage to increase.
For example, at the input voltage 202, the curve 201 would yield a
non-linear output voltage and, as a consequence, a non-constant
gain in the saturation region. The adjustment is made to alter or
shift to a different curve such that the output voltage for the
input 202 follows linearly from the linear region portion of the
curve 201. Similarly, at the input voltage 203, the curve 201 would
again yield a non-linear output voltage and a non-constant gain.
The adjustment is again made to another varied curve so that the
output voltage for the input 203 follows linearly from the linear
region portion of the curve 201.
FIG. 3 is a graph 300 illustrating an example of adaptive,
iterative envelope tracking through a series of time periods. The
graph 300 is provided as an example to illustrate adaptively
adjusting a DCDC supply to a power amplifier, such as the amplifier
110 described above.
The graph 300 depicts time on an x-axis and voltage on a y-axis.
The graph 300 includes a DCDC supply waveform 301 and an RF
envelope 302 of a transmit signal, such as the signal generated via
system 100. The graph 300 shows 4 consecutive time periods, labeled
(1) to (4).
In a first time period (1), the DCDC supply 301 somewhat tracks the
envelope 302. However, it can be seen that there is substantial
misalignment, which could be due to non-linearity or saturation. In
a second time period (2), the system 100 has incorporated some
adjustments. As a result, the DCDC supply more closely tracks the
envelope 302 in (2). In a third time period (3), the DCDC supply
tracks the envelope 302. In a fourth time period (4), the DCDC
supply 301 closely tracks the envelope 302.
FIG. 4 is a block diagram illustrating an envelope tracking
component 400 using isogain curves mapping in a communication
system. The component 400 receives a baseband signal and a
parameter signal 120 and generates a control signal 128 for a DCDC
supply component.
The component 400 can be utilized as the envelope tracking
component 104, shown above. The component 400 includes a mapping
component 430 and a digital to analog converter 432. The mapping
component 430 receives the parameter signal 120 and the baseband
signal x(t). The parameter signal 120 is based on or includes an
envelope of a transmit signal.
The mapping component 430 stores or has access to a plurality of
isogain curves, such as the curves shown in FIG. 2. The mapping
component 430 maps the parameter signal 120 and the baseband signal
to one of the isogain curves. The mapping component 430 can
determine whether the envelope is within the linear region or the
saturation region. Once mapped, the component 430 generates a
digital DCDC control adjustment 434.
The digital to analog component 432 converts the digital adjustment
434 into the control signal 128. The signal 128 is provided to a
DCDC supply, such as the supply component 106 described above,
which supplies an instantaneous DCDC supply to a power
amplifier.
FIG. 5 is a block diagram illustrating an envelope tracking
component 500 using isogain curves and/or predistoriton
coefficients in a communication system. The component 500 receives
a baseband signal and an parameter signal 120 and generates a
control signal 128 for a DCDC supply component.
The component 500 includes a curves and/or predistortion
coefficient component 536, a time delay component 538, and a
digital to analog converter 432. The component 536 receives the
parameter signal 120 and the baseband signal. The parameter signal
120 includes linearity measurements of a transmit signal.
The component 536 determines whether an adjustment is needed based
on the parameter signal 120. If an adjustment is needed, a digital
control adjustment is generated and provided to the time delay
component 538.
The time delay component 538 receives the digital control
adjustment and the parameter signal 120 and is configured to
incorporate a time synchronization adjustment into the digital
control signal 540. The digital control signal 540 is converted
into an analog control signal 128 by the digital to analog
converter 432. The analog control signal 128 can then be provided
to a DCDC supply component, such as the DCDC supply component 106
described above, which supplies an instantaneous DCDC supply to a
power amplifier.
FIG. 6 is a flow diagram illustrating a method 600 of performing
adaptive envelope tracking with time delay tracking. The method 600
can be performed at least in part using one or more of the above
described systems.
The method 600 begins at block 602, where an initial supply control
signal is generated by calibration. The initial supply control
signal is a signal that can be supplied to a DCDC supply component,
such as those described above. The initial supply control signal
includes a nominal time delay adjustment that has been determined
through calibration. The nominal time delay adjustment includes a
compromise between linearity and energy consumption.
The DCDC supply component provides a supply to a power amplifier,
which amplifies a modulated signal from a transmit path. The
transmit path generates the modulated signal from a baseband
signal.
Linearity parameter(s) or measurements are obtained from a feedback
signal during a time period or slot at block 604. The feedback
signal is generated by a feedback receiver and represents
characteristics of the transmit signal. The linearity parameters
are generated by comparing the feedback signal with a baseband
signal. Thus, the linearity parameters represent measurements of
linearity of the transmit signal. The parameters include, for
example, ACLR, EVM, and the like.
On the parameters exceeding a threshold, a control signal is
generated at block 606. The control signal includes a time delay
adjustment, which includes a time delay amount and a direction of
change. The time delay amount can be generated from a lookup table,
coefficients, and the like. The direction of the change includes
increasing or reducing. In one example, the direction is determined
from the parameters. In another example, the direction is
determined at least partially by other system characteristics
including, but not limited to, temperature, antenna impedance, and
the like. In another example, the direction is determined from
trends and/or progressions of the parameters, such as EVM, based on
previous time period delay adjustments.
On the parameters being within an acceptable range, further time
delay adjustments in the control signal are set to zero or are no
longer provided at block 608. Thus, linearity is in an acceptable
range. The method can continue at block 604 for a next time slot or
period.
While the methods provided herein are illustrated and described as
a series of acts or events, the present disclosure is not limited
by the illustrated ordering of such acts or events. For example,
some acts may occur in different orders and/or concurrently with
other acts or events apart from those illustrated and/or described
herein. In addition, not all illustrated acts are required and the
waveform shapes are merely illustrative and other waveforms may
vary significantly from those illustrated. Further, one or more of
the acts depicted herein may be carried out in one or more separate
acts or phases.
It is noted that the claimed subject matter may be implemented as a
method, apparatus, or article of manufacture using standard
programming and/or engineering techniques to produce software,
firmware, hardware, or any combination thereof to control a
computer to implement the disclosed subject matter (e.g., the
systems shown above, are non-limiting examples of circuits that may
be used to implement disclosed methods and/or variations thereof).
The term "article of manufacture" as used herein is intended to
encompass a computer program accessible from any computer-readable
device, carrier, or media. Those skilled in the art will recognize
many modifications may be made to this configuration without
departing from the scope or spirit of the disclosed subject
matter.
A communication system utilizing adaptive envelope tracking
includes a transmit path, a feedback receiver, a parameter
component and an envelope tracking component. The transmit path is
configured to generate a transmit signal. The feedback receiver is
configured to generate a feedback signal from the transmit signal.
The parameter component is configured to generate linearity
parameters from the feedback signal. The envelope tracking
component is configured to generate a supply control signal having
time delay adjustments.
In one variation, the communication system further includes a
coupler configured to provide a replica of the transmit signal to
the feedback receiver.
In another variation, any of the systems include a DCDC supply
component configured to provide a supply signal according to the
supply control signal.
Any of the above communication systems can also include a power
amplifier powered by the supply signal. The power amplifier is
configured to amplify the transmit signal from the transmit path.
The transmit signal includes time distortions.
Any of the above communications systems can also have the feedback
signal having real and imaginary components.
Any of the above communication systems, where the linearity
parameters include one or more of an adjacent channel leakage
ratio, an error vector magnitude, amplitude modulation to amplitude
modulation curves, amplitude modulation to phase modulation curves,
and time variant distortion.
Any of the above communication systems where the parameter
component is configured to generate linearity parameters from the
baseband signal and the feedback signal.
Any of the above communications systems, where the envelope
tracking component includes a time delay block configured to
generate the time delay adjustments.
Any of the above communication systems, where the time delay
adjustments include a time delay amount and a direction.
Any of the above communication systems, where the envelope tracking
component is configured to generate an initial supply signal
according to a calibration of linearity and power consumption.
Any of the above communication systems, where the envelope tracking
component is configured to track the linearity parameters over
successive time periods in order to generate the time delay
adjustments.
Any of the above communication systems, where the envelope tracking
component is configured to receive a sensor signal in order to
generate the time delay adjustments.
An envelope tracking system includes a first component and a time
delay component. The first component is configured to generate a
control signal that tracks amplitude modulation according to a
baseband signal and linearity parameters. The time delay component
is configured to generate time delay adjustments for the control
signal according to at least the linearity parameters.
In a variation of the envelope tracking system, the first component
is configured to generate the control signal by mapping the
linearity parameters and the baseband signal to isogain curves.
Any of the above envelope tracking systems, wherein the first
component is configured to generate the control signal utilizing
predistortion coefficients.
Any of the above envelope tracking systems, further including a
parameter calculation component configured to generate the
linearity parameters.
A method of performing adaptive envelope tracking with time delay
tracking is disclosed. An initial supply signal including a nominal
time adjustment is generated. One or more linearity parameters for
a current time period from a feedback signal are obtained. A
control signal having a time delay adjustment is generated on the
linearity parameters exceeding a threshold value. A control signal
without a time delay adjustment is generated on the linearity
parameters being within an acceptable range.
The above method, wherein the linearity parameters include one or
more of an error vector magnitude and an adjacent channel leakage
ratio.
Any of the above methods, where the nominal time adjustment is
based on a compromise between linearity and power consumption.
Any of the above methods, further including generating the feedback
signal from a transmit signal prior to obtaining the one or more
linearity parameters.
Although the invention has been illustrated and described with
respect to one or more implementations, alterations and/or
modifications may be made to the illustrated examples without
departing from the spirit and scope of the appended claims. For
example, although a transmission circuit/system described herein
may have been illustrated as a transmitter circuit, one of ordinary
skill in the art will appreciate that the invention provided herein
may be applied to transceiver circuits as well. Furthermore, in
particular regard to the various functions performed by the above
described components or structures (assemblies, devices, circuits,
systems, etc.), the terms (including a reference to a "means") used
to describe such components are intended to correspond, unless
otherwise indicated, to any component or structure which performs
the specified function of the described component (e.g., that is
functionally equivalent), even though not structurally equivalent
to the disclosed structure which performs the function in the
herein illustrated exemplary implementations of the invention. In
addition, while a particular feature of the invention may have been
disclosed with respect to only one of several implementations, such
feature may be combined with one or more other features of the
other implementations as may be desired and advantageous for any
given or particular application. Furthermore, to the extent that
the terms "including", "includes", "having", "has", "with", or
variants thereof are used in either the detailed description and
the claims, such terms are intended to be inclusive in a manner
similar to the term "comprising".
* * * * *